Re: [MMUSIC] Bundle offer with different ports - where to expect media?
Justin Uberti <juberti@google.com> Tue, 21 May 2013 22:39 UTC
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From: Justin Uberti <juberti@google.com>
Date: Tue, 21 May 2013 15:38:50 -0700
Message-ID: <CAOJ7v-398_MiXLWjexU0Z0xQju3A-zWuQFkWkJSLPA5UEGAu+g@mail.gmail.com>
To: Paul Kyzivat <pkyzivat@alum.mit.edu>
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Cc: mmusic <mmusic@ietf.org>, Christer Holmberg <christer.holmberg@ericsson.com>
Subject: Re: [MMUSIC] Bundle offer with different ports - where to expect media?
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Lots of discussion here; is this an accurate summary of the discussed behavior? 1) BUNDLE offerers must be able to receive on any port (until they get a BUNDLE-compatible answer) 2) Once the answer is received, bundling is activated, and BUNDLEs use the port of the first non-rejected m= line in the offer 2a) at this point, the other ports can be discarded 3) All m= lines offered in a BUNDLE must be present in the answer, unless they are rejected 3a) no selective unbundling/BUNDLE splitting is permitted On Tue, May 21, 2013 at 10:57 AM, Paul Kyzivat <pkyzivat@alum.mit.edu>wrote: > On 5/21/13 4:45 AM, Emil Ivov wrote: > >> Hey Paul, >> >> On 20.05.13, 18:09, Paul Kyzivat wrote: >> >>> On 5/20/13 10:51 AM, Emil Ivov wrote: >>> >>>> Hey Christer, >>>> >>>> On 20.05.13, 17:16, Christer Holmberg wrote: >>>> >>>>> Hi, >>>>> >>>>> What happens when the offerer knows the answerer has bundle >>>>>>>> support, sends all m-lines with the same port, then the >>>>>>>> answerer splits the first line away from the bundle? Would the >>>>>>>> answerer still send everything to the same port? >>>>>>>> >>>>>>> >>>>>>> We discussed this week, >>>>>>> >>>>>>> Yes, sorry, I didn't follow this closely. >>>>>> >>>>>> and the outcome (at least my read of it :) was that the answerer >>>>>>> is not allowed to split any m- lines away from the bundle in this >>>>>>> case. Instead the answerer will have to send a new offer for the >>>>>>> split, allowing new ports to be negotiated at both ends. >>>>>>> >>>>>> >>>>>> OK, so shouldn't the same thing happen in the case with different >>>>>> ports? >>>>>> >>>>> >>>>> I suggested that it should never be allowed to split an m- line from >>>>> a bundle group in an answer, but others had other opinions. >>>>> >>>> >>>> I don't see how we could allow it in one case and disallow it in the >>>> other. The only difference between the two cases is how informed the >>>> offerer is about the answerers bundle support capabilities and I don't >>>> really understand why this would influence the decision to allow >>>> splitting bundles one way or the other. >>>> >>> >>> It is a different case because the same port *can't* both be used as the >>> bundle port and a port for an unbundled m-line. >>> >> >> Why not? Obviously the offerer was prepared to demultiplex traffic >> there. Why wouldn't it be able to continue doing so even if the answerer >> would prefer to receive it separately? >> > > The point of wanting the one line unbundled is so that it can be > *received* on a different address/port. Perhaps there is a separate device > or process that will be supporting that one, that must be reached at its > own addr/port. > > Unless you expect that this would have a common addr/port on the offering > side and different addr/ports on the answering side. But we investigated > that approach early in the bundle discussions, and gave it up. > > > Note that I am not defending such an approach. I'd much prefer that >> splitting is only allowed when re-offering. >> >> HOWEVER, it would still not help in the case where the 1st m- line is >>>>> rejected. >>>>> >>>> >>>> Well, how about looking at it this way: the offerer specifies a bundle >>>> port in the first m=line. This also happens to be the port for the first >>>> media line but the two are different things and just happen to have the >>>> same value for reasons related to syntax and convenience. >>>> >>>> A bundle supporting answerer should understand this. After receiving the >>>> offer that answerer has learned the bundle port number. Rejecting the >>>> first m=line in the answer does not change this. >>>> >>> >>> There are many reasons that an answerer may reject an m-line. >>> It is *possible* that it is rejecting it because it has a problem with >>> the address (c=) for the m-line in the offer. If so, then if you insist >>> on using it as the bundle address, even if the m-line is refused, then >>> there is no way for the answerer to refuse it. >>> >>> (*Why* it would have a problem is an open question. Maybe its IPv6 and >>> the answerer can't use it, or maybe its an FQDN and it can't be >>> resolved. I realize this is unlikely. But making the assumption that the >>> address must be acceptable to the answerer is IMO not a good idea.) >>> >> >> Aha! That's a good point. >> >> Still, the thing that I don't quite understand is: if the answerer has a >> problem with the c= line, how could that problem only apply to the first >> m= line and not to the entire bundle? >> > > Presumably this would only happen if the c= for were not all the same in > the offer. Certainly that is possible. When allocating "ports" for each > m-line one might also end up with different addresses. > > > Of course the answer would come with the first m=line having a 0 port >>>> but the offerer would then just learn the bundle port number at the >>>> first m=line with a non-zero port. >>>> >>> >>> I presume you must have a motivation for wanting to go this way. >>> Are you thinking this will simplify the implementation? >>> >> >> No. The implementation is going to be slightly more complicated indeed >> because instead of having one bundle demuxing socket and two regular >> ones (well ... if rtcp demuxing counts as regular) you would have three >> of them. I don't think this would be particularly horrifying in terms of >> complexity though. >> >> Still, I think being consistent about the ports where one could get >> multiplexed data is a good thing, and it could help (humans) when >> analysing traffic and debugging network issues. >> > > Consistency is good. But isn't it just as consistent to say that the first > *accepted* m-line defines the bundle addr/port as it is to say that the > first offered m-line? > > Thanks, > Paul > > > ______________________________**_________________ > mmusic mailing list > mmusic@ietf.org > https://www.ietf.org/mailman/**listinfo/mmusic<https://www.ietf.org/mailman/listinfo/mmusic> >
- [MMUSIC] Bundle offer with different ports - wher… Christer Holmberg
- Re: [MMUSIC] Bundle offer with different ports - … Emil Ivov
- Re: [MMUSIC] Bundle offer with different ports - … Hutton, Andrew
- Re: [MMUSIC] Bundle offer with different ports - … Emil Ivov
- Re: [MMUSIC] Bundle offer with different ports - … Christer Holmberg
- Re: [MMUSIC] Bundle offer with different ports - … Paul Kyzivat
- Re: [MMUSIC] Bundle offer with different ports - … Emil Ivov
- Re: [MMUSIC] Bundle offer with different ports - … Christer Holmberg
- Re: [MMUSIC] Bundle offer with different ports - … Hutton, Andrew
- Re: [MMUSIC] Bundle offer with different ports - … Emil Ivov
- Re: [MMUSIC] Bundle offer with different ports - … Christer Holmberg
- Re: [MMUSIC] Bundle offer with different ports - … Emil Ivov
- Re: [MMUSIC] Bundle offer with different ports - … Paul Kyzivat
- Re: [MMUSIC] Bundle offer with different ports - … Emil Ivov
- Re: [MMUSIC] Bundle offer with different ports - … Christer Holmberg
- Re: [MMUSIC] Bundle offer with different ports - … Emil Ivov
- Re: [MMUSIC] Bundle offer with different ports - … Cullen Jennings (fluffy)
- Re: [MMUSIC] Bundle offer with different ports - … Paul Kyzivat
- Re: [MMUSIC] Bundle offer with different ports - … Paul Kyzivat
- Re: [MMUSIC] Bundle offer with different ports - … Emil Ivov
- Re: [MMUSIC] Bundle offer with different ports - … Justin Uberti
- Re: [MMUSIC] Bundle offer with different ports - … Justin Uberti
- Re: [MMUSIC] Bundle offer with different ports - … Eric Rescorla
- Re: [MMUSIC] Bundle offer with different ports - … Emil Ivov
- Re: [MMUSIC] Bundle offer with different ports - … Martin Thomson
- Re: [MMUSIC] Bundle offer with different ports - … Justin Uberti
- Re: [MMUSIC] Bundle offer with different ports - … Christer Holmberg
- Re: [MMUSIC] Bundle offer with different ports - … Paul Kyzivat
- Re: [MMUSIC] Bundle offer with different ports - … Kevin Dempsey
- Re: [MMUSIC] Bundle offer with different ports - … Paul Kyzivat
- Re: [MMUSIC] Bundle offer with different ports - … Justin Uberti
- Re: [MMUSIC] Bundle offer with different ports - … Justin Uberti
- Re: [MMUSIC] Bundle offer with different ports - … Paul Kyzivat
- Re: [MMUSIC] Bundle offer with different ports - … Dale R. Worley
- Re: [MMUSIC] Bundle offer with different ports - … Christer Holmberg
- Re: [MMUSIC] Bundle offer with different ports - … Suhas Nandakumar
- Re: [MMUSIC] Bundle offer with different ports - … Christer Holmberg
- Re: [MMUSIC] Bundle offer with different ports - … Emil Ivov
- Re: [MMUSIC] Bundle offer with different ports - … Christer Holmberg
- Re: [MMUSIC] Bundle offer with different ports - … Cullen Jennings (fluffy)
- Re: [MMUSIC] Bundle offer with different ports - … Cullen Jennings (fluffy)
- [MMUSIC] When a bundle offer is forked Paul Kyzivat
- Re: [MMUSIC] When a bundle offer is forked Parthasarathi R
- Re: [MMUSIC] When a bundle offer is forked Paul Kyzivat
- Re: [MMUSIC] Bundle offer with different ports - … Martin Thomson
- Re: [MMUSIC] When a bundle offer is forked Martin Thomson
- Re: [MMUSIC] Bundle offer with different ports - … Paul Kyzivat
- Re: [MMUSIC] When a bundle offer is forked Paul Kyzivat
- Re: [MMUSIC] When a bundle offer is forked Dale R. Worley
- Re: [MMUSIC] Bundle offer with different ports - … Martin Thomson
- Re: [MMUSIC] When a bundle offer is forked Christer Holmberg
- Re: [MMUSIC] When a bundle offer is forked Parthasarathi R
- Re: [MMUSIC] When a bundle offer is forked Christer Holmberg
- Re: [MMUSIC] Bundle offer with different ports - … Paul Kyzivat
- Re: [MMUSIC] When a bundle offer is forked Parthasarathi R
- Re: [MMUSIC] When a bundle offer is forked Christer Holmberg
- Re: [MMUSIC] Bundle offer with different ports - … Martin Thomson
- Re: [MMUSIC] Bundle offer with different ports - … Martin Thomson
- Re: [MMUSIC] Bundle offer with different ports - … Paul Kyzivat
- Re: [MMUSIC] Bundle offer with different ports - … Martin Thomson
- Re: [MMUSIC] When a bundle offer is forked Cullen Jennings (fluffy)